The invention relates to an apparatus for the entry of hot gas into a heating surface tube of a waste heat boiler having an outer tube connected to the boiler wall, in particular to the tube base, and further having inner or inlet tube that is connected to the outer tube by means of a rounded reversing cap to form an inlet port for the hot gas and that is surrounded by the outer tube at a given distance and that has a cylindrical or conically narrowing inflow section and an outflow section that is connected to the heating surface tube, and having a coolant transport tube that is disposed between the outer tube and the inner tube and that extends into the vicinity of the reversing cap.
In waste heat boilers or heat exchangers, hot gases (such as synthesis gases from partial oxidation systems) are cooled by coolants, in most cases generating steam. The heat exchangers preferably consist of a plurality of straight, curved or helical heating surface systems that are connected to each other in parallel and that are formed by a plurality of heating surface tubes.
The heat exchanger inlet areas that are exposed to the hot gas, in particular, are subjected to very high thermal loads. Because of the high system pressure of the heat-absorbing medium (such as boiling water), additional high mechanical loads result that, among other things, also must be removed by the inlet areas or the devices provided for the hot gas to enter the heating surface tubes.
The publication “Verfahrenstechnik: Anlagen-und Apparatebau, Komponenten und Teilkreisläufe” [process engineering: system and apparatus design, components and subcircuits] (1986), page 19, published by the firm of L. & C. Steinmüller, discloses an apparatus of the type defined in the preamble. In this prior-art apparatus, components are present-and this applies in particular to the reversing caps where the gas enters the apparatus—at which unacceptably high surface temperatures and/or unacceptably high mechanical and thermal loads can occur. In addition, these components can lead to a limiting of the gas-side flow rate of each individual device used for the entry of hot gas into a heating surface tube of a waste heat boiler, and, as a consequence, to the limiting of the gas-side flow rate in the downstream heating surface tube and, thus, in the entire waste heat boiler. High surface temperatures result in a wide range of risks with regard to various corrosion mechanisms.